SU951474A1 - Electron beam apparatus - Google Patents

Description

one

The invention relates to an electronic technique, namely, an electron-beam instrument (EBT) technique and can be used to improve the 3JV1 design, reduce the likelihood of breakdowns, to the high-voltage electrodes of the electron-optical system (EOS) and the power of these breakdowns in case of their occurrence.

Providing high demands on luminance brightness, resolution, recording speed and other parameters of EBT in many cases is possible only with the use of 15 high voltages applied to certain EOS electrodes. Most tenaciously, this tendency can be traced in color and projection tube tubes, which are powered by M voltages of 25-75 kV. Frequently, an increase in supply voltages occurs with a simultaneous decrease in the throat diameter, an increase in the diameter of the EC (electrodes, an increase in the gettering surface, etc.) All this leads to the formation of local electric fields with a large potential gradient, the occurrence and uncontrolled redistribution. charges on insulating surfaces, the appearance of areas with increased emissivity, and other phenomena that provoke breakdown.

During the breakdown of currents, the discharge reaches large values of several tens to hundreds of amperes. Allocated power is the cause of the destruction of contacts, heating of EOS parts, additional gas release, etc. Possible and out of order, power sources. ESC

The known traditional methods of preventing breakdowns are reduced to the complication of the design and technology of manufacturing EBD: the use of spark arresters, increasing the frequency of processing EOS electrodes and EBR elements. Technological is also used — the reception of high-voltage burn-through, the so-called stiffness, in which, as a result of deliberate breakdowns caused by applying a voltage increased to the device that is higher than the operating value, some defects are conductive, but breakdowns C However, these methods, despite the complexity, design and technology manufacture of the device, leading to an increase in its cost, however, does not provide for the complete elimination of breakdowns, and stiffness may appear as a reason for the device’s failure due to s high voltage, and the occurrence of new defects in generating subsequent breakdowns in a previously normal operating appliance. EBTs are also known, in which the traditionally low-resistance coating connecting the last EOS electrode with the anode terminal on the glass shell is replaced by a coating with a relatively high resistance of hundreds of ohms. The resistor enters the discharge circuit and limits the current and the motor breakdown. The coating is applied to the tapered portion of the shell and the neck of the device. A more detailed study of the discharge circuit shows that not only the presence of a damping resistor is important, but also the capacitances that this resistor forms with other elements of the device must be taken into account. From this point of view, the extended coating having a large surface is not very profitable, since it forms considerable own capacities. In addition, in order to successfully suppress the discharge, the quenching resistor must be large — on the order of hundreds or thousands of kilohms. The manufacture of such a high resistance coating, pd-. native across the entire area located inside the bulb, is a complex technological setting of the LINE and the power of the steady-state discharge is determined by the characteristics of the damping resistor. Therefore, it must meet certain requirements, the main ones being the uniformity of resistance across all coverage areas and the stability of its parameters from the instrument to the instrument. Local unevenness of resistance can lead to uneven distribution of the potential and heat when the discharge current passes. This in turn may be caused by the overlap, i.e. shorting the discharge of part or all of the damping resistor. At the same time, the usual technology of applying continuous coatings on the internal cavities of an EBT n makes it possible to obtain damping resistors that meet these requirements. In the known device for reducing the parasitic capacitances of the damping resistor, it is made in the form of a conductive coating deposited on a ceramic holder antenna getter. Since the damping resistor is; essentially, it is a separate element; in its manufacture a more advanced technology can be used, which makes it homogeneous. Along with positive properties, the manufacture of a damping resistor as a separate element placed inside an electronic ballast has a number of drawbacks: the impossibility of using such a solution in other types of electronic ballast, except for color kinescopes; . significant complication of the design and technology of manufacturing EBD; decrease in mechanical strength of EBR. . The purpose of the invention is to increase reliability by increasing resistance to high-voltage breakdowns. This goal is achieved by the fact that in an EBR containing a vacuum shell with an EOS located inside it, the high-voltage electrode of which is electrically connected to the anode terminal on the shell through a damping resistor, the latter is made in the form of a spiral of resistive material deposited on the inner surface of the neck of the envelope, with the length of the helix being 1-2 neck diameters. The drawing shows one of the possible uses of the invention, the EBD contains a vacuum glass shell 1 with a neck 2 in which the EOS containing the cathode 3, the modulator C, the accelerating electrode 5 focusing is placed. electrode 6 and high voltage electrode 7. For normal operation of the device, a high voltage is required on the last electrode 7, usually supplied through the anode terminal 8 on the sheath 1. High voltage electrode

7 electrically connected to the output

8through sections of low-resistance coatings

9 and 10, section 11 of a helix made of resistive material. The device has a luminescent screen 12 and an outer conductive coating 13. The lower limit of the resistance of the spiral is determined by the need for effective discharge current quenching, the upper one by the need to apply almost all of the high voltage to the electrode 7 (the resistance of the spiral forms a divider with a series-connected leakage resistance between

electrodes 6 and 7L. Usually the value of the resistance of the helix should lie in the range of 0.1-3Mem.

The difference in the use of a spiral as a high-resistance coating on the inner surface of the shell neck in extended electrostatic lenses (for example, bipotential) is that, in the absence of a breakdown in a normal mode of operation, there is no voltage drop on the spiral — it is equipotential and shell and high-voltage electrode. Only in the case of a breakdown, the spiral begins to work in the mode of quenching the breakdown, while on the spiral of the extended pinz in the course of its operation there is a drop in voltage and. -.

These helix length ratios are due to the following.

If the length of the spiral along the axis is less than the diameter of the neck, then the breakdown of the high voltage gap may break the spiral along the surface of the neck and, therefore, the discharge current of the high voltage gap will not be limited to the spiral.

If the length of the helix is more than two neck diameters, then the parasitic capacitance of the damping resistance will greatly increase and the current will be high, resulting in negative effects & ELP. And radio circuit.

In the absence of a breakdown voltage supplied from an external source to terminal 8, it is practically applied to a resistive divider formed by the resistance of the spiral and the leakage resistance between electrodes 7 and 6. Since the leakage resistance of the vacuum gap is substantially greater than the resistance of the spiral, almost all The high voltage source is applied to the high voltage EOS electrode. The electron beam falling on the screen is closed at a high-voltage source, a spiral is mined.

When an operating mode is established, the charge of parasitic containers occurs. However, the small area of the helix and the large distances between its ends cause a small amount of these capacities, and consequently also a small amount of energy stored in them. Therefore, in the event of a breakdown between the electrodes 6 and 7, the magnitude of the initial current is insignificant. In addition, the initial current jump, which can be disrupted by electronic circuits, is hampered not only by the resistance of the spiral, but also by its inductance. All this leads to the fact that the discharge does not develop and goes out at the initial stage, causing almost no negative consequences. This is also facilitated by the uniform, uniform along the length of the resistance of the spiral.

In general, the use of the invention improves the reliability of EBR, simplifies the design of the device and the technology of its manufacture, increases the mechanical strength of the instrument, and also increases the percentage of yield of EBR during the production process.

The invention can be used in all high-voltage ELP.

Claims (2)

1. Miller V.A., Kurakin L.A. Foster tubes, M., Energie, 1971, pp.82-92. . 2.Schwartz I.M, and all Recent 5 developments in are supperession for picture tubes. - IEEE Trans CE .v 25, 1979. 7 3 11 W 3 ff 5 .1 6 I I L